Matthew 21:4

Now this is come to pass that it might be fulfilled which was spoken through the prophet, saying, Tell ye the daughter of Zion, Behold, thy King cometh unto thee Meek, and riding upon an ass, And upon a colt the foal of an ass.

This prophecy from Zechariah 9:9 was generally understood as a reference to the Messiah; and Jesus deliberately and conspicuously fulfilled it by the events recorded here. By identifying himself in such a manner, Christ definitely laid claim to the office of Messiah, setting the stage for his public proclamation as the true King.